recipient_delimiter keeps resetting

[useopenid]

We have a user just moved to zimbra who's been using +tag address extensions extensively. I've manually added the +: "recipient_delimiter = +", but it keeps getting reset. I'm not sure why normal zimbra web interface account administration would be reconfiguring postfix, but it's a real problem. Suggestions?

[useopenid]

The Admin Guide does have this warning:

Important: Do not modify the Postfix configuration files directly! Some of the Postfix files are rewritten when changes are made in the administration console. Any changes you make will be overwritten.

but it doesn't say where you're supposed to make such changes. Something pointed me at zmmta.cf, which implies an ldap variable:

VAR zimbraMtaRecipientDelimiter
POSTCONF recipient_delimiter VAR zimbraMtaRecipientDelimiter

and the admin guide does say ldap holds things now, but nope:

prov> ms zmail-mta01.peak.org zimbraMtaRecipientDelimiter +
ERROR: service.INVALID_REQUEST (invalid request: LDAP schema violation: [LDAP: error code 65 - attribute 'zimbraMtaRecipientDelimiter' not allowed]) (cause: javax.naming.directory.SchemaViolationException [LDAP: error code 65 - attribute 'zimbraMtaRecipientDelimiter' not allowed])

OK, let's try zmlocalconfig:

zmlocalconfig -e recipient_delimiter='+'

That at least modifies localconfig.xml, however, in zmmtaconfig.log after restarting zimbra:

Thu Sep 30 11:47:01 2010 Skipping Configuration for server localhost update.
Thu Sep 30 11:47:01 2010 gs:localhost ERROR: account.NO_SUCH_SERVER (no such server: localhost)
Thu Sep 30 11:47:01 2010 Sleeping...Key lookup failed.
Thu Sep 30 11:49:04 2010 zmmtaconfig started on zmail-mta01.peak.org with loglevel=3 pid=6543

and main.cf is unchanged.

It would be really nice if when docs say something like "don't change this here!", they include "do it over *here*" and if you have to do something to actually get the change to take effect, that's included as well...